GE/FE Head Differences
There are generally two types of cylindar heads that Toyota uses
in its gas-powered vehicles. These are represented in the engine
code (all-non RWD Celicas) by either a F or a G in the engine code.
The F-head (high efficency below) has a design which optimizes mid
range torque/horsepower. The G-head (high performance), in contrast,
produces significantly more horsepower but at a much higher RPM.
Since most driving takes place between 500-4000RPMs, the F-head
holds the drivability and mileage advantage over the GE head. As
such this design shows its dominance in most Toyota vehicles in
the US. When it comes to performance the G-head will is superior
hands down.The following diagrams from the book "Toyota Engine
Technology" published by Toyota in 1989 illustrate the differences
in Toyota's data between the two engines.
you can see in this image the G-head is designed with a wider valve
angle (50° as opposed to 22-25°) and a different shaped
image illustrates the side profiles of the 3S engine block with
the G- & F-heads. The size difference is most likely due to
the slave-twin cam design of the F-head as opposed to the true twin
cam design of the G-head.
is the torque curve of a F-head (high-efficiency twin cam) as opposed
to a G-head (Sports-type twin cam).
the power differences between the F-head(middle) and G-head engines.
I believe this graph illustrates the various Toyota engines with
either head (circa 1989).
all images from
Toyota Engine Technology ©1989 Toyota